The present invention relates to a mechanism for preventing unintended selection of a reverse gear in a manual transmission of a vehicle.
The invention specifically relates to a manual transmission in which the selection of speed ranges or the shifting of gear ratios is effected by the operation of a control lever to rotate or to shift the fork rod axially. In such a transmission, having its shift pattern such that the reverse gear shift position is aligned on a linear shift line of the control lever with a forward gear shift position, it is possible to unintentionally select the reverse position erroneously during the select or shift operation from the forward gear shift position to another forward gear shift position. In such erroneous gear selection of the reverse gear position it is obvious that a large noise of gear coupling occurs and in some case breakdown of the gear system may result.
A mechanism for preventing misselection of the reverse gear position is known. One example of a prior art device is shown in FIG. 1. The mechanism comprises a circular plate 51 having a hole 51a through which the lower end of the control lever 50 is extended. A cam 54 is pivotally mounted on a pin 52 secured to the plate 51 with an intervention of a coil spring 53. This circular plate 51 is mounted on the housing 55 after passing around the control lever 50 and is fixed in position by means of a cap 56. The operation of this mechanism can better be seen from FIG. 2. In FIG. 2, 1st, 2nd, 3rd, 4th and 5th show the position of the control lever in the respective forward steps and R shows the reverse position. When a driver wishes to operate the control lever 50 to downshift from the forward 5th speed range, the control lever 50 abuts against an end 54a of the cam 54 so that the cam 54 rotates counterclockwisely as shown in the drawing and the other end 54b comes in contact with the housing 55 as indicated by the double dotted line. By this means a linear shift operation of the control lever 50 is prevented and the possible misselection of the reverse gear shift position is avoided. However, the assembling of this mechanism is troublesome since the circular plate 51 must be mounted onto the housing 55 after inserting the control lever through its hole 51a and thereafter the circular plate must be fixed by a cap 56 and thereafter a control lever boot not shown in the drawing must be applied thereon. The disassembling of the same mechanism is also troublesome. Therefore, this mechanism increases the cost in manufacturing a vehicle.